1. Field of the Invention
The present invention relates to a production method of a polyester by using a microorganism.
2. Related Background Art
Microbial polyesters represented by poly 3-hydroxybutyrate (PHB) have a remarkable feature that they are biologically degradable, differing from the synthetic polymers made from petroleum.
Synthetic polymers have been used as plastics etc. for a long time. On disposal, however, this feature of hard-to-decompose makes them accumulated in waste-disposal facilities, or when they are burned, harmful substances such as dioxin and endocrine-disruptors are generated to cause environmental pollution.
On the other hand, polyesters produced by microorganisms (hereinafter referred to as xe2x80x9cmicrobial polyestersxe2x80x9d) can be biologically degraded to be incorporated in a natural recycling system, usable as environment-maintaining plastics. They also have a potential as soft materials for medical use (Japanese Patent Application Laid-Open No. 5-159).
Heretofore, various bacteria have been reported to produce and accumulate PHB or copolymers of other hydroxyalkanoic acids in the cells (Handbook of Biodegradable Plastics, ed. by Biodegradable Plastics Society, published by N.T.S., p. 178-197 (1995)).
Recently, for industrial use of such poly hydroxyalkanoic acids (PHA), various attempts have been done to make the microorganisms produce modified PHA comprised of unusual monomer units for broader physicochemical properties.
One of these attempts, Japanese Patent Application Laid-Open No. 5-30980, discloses that Pseudomonas fluorescence FA-031 (FERM P-3433) can produce copolymers of poly hydroxyfatty acid esters made of monomer units of C4 to C16, when the cells are cultured using oleic acid, triolein (olive oil) or triglyceride as a carbon source under nitrogen starvation. The presence of carbon-carbon double bonds were confirmed in C14 and C16 units.
Further, it discloses that when linoleic acid is used as a substrate, the produced polyester is comprised of units of C4 to C16, the presence of double bond was confirmed in units of C10, C12, C14, and C16, and when xcex1-linolenic acid is used as a substrate, the produced polyester is comprised of units of C4 to C16, the presence of double bonds were confirmed in units of C8, C10, C12, C14, and C16.
A method to produce PHA containing units of 3-hydroxyoctenoic acid and 3-hydroxyhexenoic acid is disclosed in Int. J. Biol. Macromol. Vol,12 p. 85-91 (1989), where Pseudomonas oleovorans ATCC 29347 is grown using 3-hydroxy-6-octenoic acid or 3-hydroxy-7-octenoic acid as a substrate.
A method to produce PHA containing units of 3-hydroxydecenoic acid and 3-hydroxytetradecenoic acid is disclosed in Appl. Environ. Microbiol. (1992) Vol. 58(2) p. 536-544, where Pseudomonas putida KT2442 is grown using glucose, fructose and glycerol as substrates.
A method to produce PHA containing units of 3-hydroxyoctenoic acid and 3-hydroxyhexenoic acid is disclosed in Polymer, Vol 35(10) (1994) p. 2090-2097, where Pseudomonas oleovorans ATCC 29347 is grown using n-octane and 1-octene as substrates.
A method to produce PHA containing units of 3-hydroxydecenoic acid and 3-hydroxytetradecenoic acid is disclosed in Int. J. Biol. Macromol. 23 (1994) p. 61-72 where Pseudomonas resinovorans NRRL B-2649 is grown using tallow as a substrate.
Although various methods have been studied to produce PHA having carbon-carbon double bonds in their side chains using microorganisms as described above, the inventors have come to think that more variety of the culture conditions and substrates are required for practical use. At present, studies on the use of organic substrate materials derived from relatively inexpensive minerals such as petroleum are not at least sufficient.
According to one embodiment of the present invention, there is provided a method for producing microbial polyester which comprises a step of growing a microorganism capable of producing a polyester in a medium containing 1-hexene as a sole carbon source.
Preferably, at least one monomer unit constituting the polyester is a hydroxyfatty acid having a carbon double bond, more preferably, at least one of 3-hydroxyhexenoic acid and 3-hydroxyocteinoic acid.
Preferably, the microorganism is a bacterium of genus Pseudomonas, more preferably, Pseudomonas cichorii YN2 (FERM BP-7375).
The method of the present invention further comprises a step of recovering the polyester product from the microorganism in the culture medium.
The method of the present invention enables the production of poly hydroxyalkanoate containing 3-hydroxyfatty acid having a double bond in the side chain by using 1-hexene as a sole carbon source.